This is what a second-chance letter from the President of the United States looks like

REUTERS/Jonathan ErnstU.S. President Barack Obama winks at visitors and reporters watching as he returns via Marine One helicopter after travel from Tennessee to the White House in Washington July 1, 2015.

President Barack Obama on Monday commuted prison sentences for dozens of inmates across the US.

The White House announced that 46 prisoners — most of them convicted of non-violent, drug-related crimes — would have their sentences commuted.

“These men and women were not hardened criminals, but the overwhelming majority have been sentenced for at least 20 years, or in some cases decades ago,” Obama said in a video address.

“Their punishments did not meet the crime,” he added. The White House said the 46 commutations represent the largest number authorised by a president in “decades.”

In a letter to prisoner Jerry Allen Bailey, one of the inmates whose sentences was shortened on Monday, Obama commended the prisoner’s lifestyle changes, and told Bailey to set a good example outside of prison.

“I am granting your commutation because you have demonstrated that you can turn your life around,” Obama wrote to Bailey, who was convicted for conspiracy to violate narcotics laws. “Now it is up to your to make the most of this opportunity.

“It will not be easy, and will confront many who doubt people with criminal records can change,” Obama said. “I believe in your ability to prove the doubters wrong, and change your life for the better.”

The commutations come on the heels of a larger push by the Obama administration to overhaul the criminal justice system, an issue that has seen bipartisan support in Congress. The Obama administration has repeatedly said that the current laws are wasteful and unusually tough on non-violent drug offenders, and it sees the issue as one of the few on which Republicans and Democrats broadly agree.

At an NAACP event later this week, Obama is expected to call for sentencing reform. And on Thursday, Obama will visit a jail in Oklahoma City, becoming the first sitting president to visit a prison.

“A lot of people have become aware of the inequities in the criminal justice system, the fact that we spend over $US80 billion a year incarcerating people oftentimes who’ve only been engaged in non-violent drug offenses,” Obama said in the video address.